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 * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package java.lang.invoke;

import sun.invoke.util.Wrapper;
import java.lang.ref.SoftReference;

import static java.lang.invoke.MethodHandleStatics.*;

/**
 * Shared information for a group of method types, which differ only by reference types, and
 * therefore share a common erasure and wrapping. <p> For an empirical discussion of the structure
 * of method types, see <a href="http://groups.google.com/group/jvm-languages/browse_thread/thread/ac9308ae74da9b7e/">
 * the thread "Avoiding Boxing" on jvm-languages</a>. There are approximately 2000 distinct erased
 * method types in the JDK. There are a little over 10 times that number of unerased types. No more
 * than half of these are likely to be loaded at once.
 *
 * @author John Rose
 */
final class MethodTypeForm {

  final int[] argToSlotTable, slotToArgTable;
  final long argCounts;               // packed slot & value counts
  final long primCounts;              // packed prim & double counts
  final MethodType erasedType;        // the canonical erasure
  final MethodType basicType;         // the canonical erasure, with primitives simplified

  // Cached adapter information:
  @Stable
  final SoftReference<MethodHandle>[] methodHandles;
  // Indexes into methodHandles:
  static final int
      MH_BASIC_INV = 0,  // cached instance of MH.invokeBasic
      MH_NF_INV = 1,  // cached helper for LF.NamedFunction
      MH_UNINIT_CS = 2,  // uninitialized call site
      MH_LIMIT = 3;

  // Cached lambda form information, for basic types only:
  final @Stable
  SoftReference<LambdaForm>[] lambdaForms;
  // Indexes into lambdaForms:
  static final int
      LF_INVVIRTUAL = 0,  // DMH invokeVirtual
      LF_INVSTATIC = 1,
      LF_INVSPECIAL = 2,
      LF_NEWINVSPECIAL = 3,
      LF_INVINTERFACE = 4,
      LF_INVSTATIC_INIT = 5,  // DMH invokeStatic with <clinit> barrier
      LF_INTERPRET = 6,  // LF interpreter
      LF_REBIND = 7,  // BoundMethodHandle
      LF_DELEGATE = 8,  // DelegatingMethodHandle
      LF_DELEGATE_BLOCK_INLINING = 9,  // Counting DelegatingMethodHandle w/ @DontInline
      LF_EX_LINKER = 10,  // invokeExact_MT (for invokehandle)
      LF_EX_INVOKER = 11,  // MHs.invokeExact
      LF_GEN_LINKER = 12,  // generic invoke_MT (for invokehandle)
      LF_GEN_INVOKER = 13,  // generic MHs.invoke
      LF_CS_LINKER = 14,  // linkToCallSite_CS
      LF_MH_LINKER = 15,  // linkToCallSite_MH
      LF_GWC = 16,  // guardWithCatch (catchException)
      LF_GWT = 17,  // guardWithTest
      LF_LIMIT = 18;

  /**
   * Return the type corresponding uniquely (1-1) to this MT-form.
   * It might have any primitive returns or arguments, but will have no references except Object.
   */
  public MethodType erasedType() {
    return erasedType;
  }

  /**
   * Return the basic type derived from the erased type of this MT-form.
   * A basic type is erased (all references Object) and also has all primitive
   * types (except int, long, float, double, void) normalized to int.
   * Such basic types correspond to low-level JVM calling sequences.
   */
  public MethodType basicType() {
    return basicType;
  }

  private boolean assertIsBasicType() {
    // primitives must be flattened also
    assert (erasedType == basicType)
        : "erasedType: " + erasedType + " != basicType: " + basicType;
    return true;
  }

  public MethodHandle cachedMethodHandle(int which) {
    assert (assertIsBasicType());
    SoftReference<MethodHandle> entry = methodHandles[which];
    return (entry != null) ? entry.get() : null;
  }

  synchronized public MethodHandle setCachedMethodHandle(int which, MethodHandle mh) {
    // Simulate a CAS, to avoid racy duplication of results.
    SoftReference<MethodHandle> entry = methodHandles[which];
    if (entry != null) {
      MethodHandle prev = entry.get();
      if (prev != null) {
        return prev;
      }
    }
    methodHandles[which] = new SoftReference<>(mh);
    return mh;
  }

  public LambdaForm cachedLambdaForm(int which) {
    assert (assertIsBasicType());
    SoftReference<LambdaForm> entry = lambdaForms[which];
    return (entry != null) ? entry.get() : null;
  }

  synchronized public LambdaForm setCachedLambdaForm(int which, LambdaForm form) {
    // Simulate a CAS, to avoid racy duplication of results.
    SoftReference<LambdaForm> entry = lambdaForms[which];
    if (entry != null) {
      LambdaForm prev = entry.get();
      if (prev != null) {
        return prev;
      }
    }
    lambdaForms[which] = new SoftReference<>(form);
    return form;
  }

  /**
   * Build an MTF for a given type, which must have all references erased to Object.
   * This MTF will stand for that type and all un-erased variations.
   * Eagerly compute some basic properties of the type, common to all variations.
   */
  @SuppressWarnings({"rawtypes", "unchecked"})
  protected MethodTypeForm(MethodType erasedType) {
    this.erasedType = erasedType;

    Class<?>[] ptypes = erasedType.ptypes();
    int ptypeCount = ptypes.length;
    int pslotCount = ptypeCount;            // temp. estimate
    int rtypeCount = 1;                     // temp. estimate
    int rslotCount = 1;                     // temp. estimate

    int[] argToSlotTab = null, slotToArgTab = null;

    // Walk the argument types, looking for primitives.
    int pac = 0, lac = 0, prc = 0, lrc = 0;
    Class<?>[] epts = ptypes;
    Class<?>[] bpts = epts;
    for (int i = 0; i < epts.length; i++) {
      Class<?> pt = epts[i];
      if (pt != Object.class) {
        ++pac;
        Wrapper w = Wrapper.forPrimitiveType(pt);
        if (w.isDoubleWord()) {
          ++lac;
        }
        if (w.isSubwordOrInt() && pt != int.class) {
          if (bpts == epts) {
            bpts = bpts.clone();
          }
          bpts[i] = int.class;
        }
      }
    }
    pslotCount += lac;                  // #slots = #args + #longs
    Class<?> rt = erasedType.returnType();
    Class<?> bt = rt;
    if (rt != Object.class) {
      ++prc;          // even void.class counts as a prim here
      Wrapper w = Wrapper.forPrimitiveType(rt);
      if (w.isDoubleWord()) {
        ++lrc;
      }
      if (w.isSubwordOrInt() && rt != int.class) {
        bt = int.class;
      }
      // adjust #slots, #args
      if (rt == void.class) {
        rtypeCount = rslotCount = 0;
      } else {
        rslotCount += lrc;
      }
    }
    if (epts == bpts && bt == rt) {
      this.basicType = erasedType;
    } else {
      this.basicType = MethodType.makeImpl(bt, bpts, true);
      // fill in rest of data from the basic type:
      MethodTypeForm that = this.basicType.form();
      assert (this != that);
      this.primCounts = that.primCounts;
      this.argCounts = that.argCounts;
      this.argToSlotTable = that.argToSlotTable;
      this.slotToArgTable = that.slotToArgTable;
      this.methodHandles = null;
      this.lambdaForms = null;
      return;
    }
    if (lac != 0) {
      int slot = ptypeCount + lac;
      slotToArgTab = new int[slot + 1];
      argToSlotTab = new int[1 + ptypeCount];
      argToSlotTab[0] = slot;  // argument "-1" is past end of slots
      for (int i = 0; i < epts.length; i++) {
        Class<?> pt = epts[i];
        Wrapper w = Wrapper.forBasicType(pt);
        if (w.isDoubleWord()) {
          --slot;
        }
        --slot;
        slotToArgTab[slot] = i + 1; // "+1" see argSlotToParameter note
        argToSlotTab[1 + i] = slot;
      }
      assert (slot == 0);  // filled the table
    } else if (pac != 0) {
      // have primitives but no long primitives; share slot counts with generic
      assert (ptypeCount == pslotCount);
      MethodTypeForm that = MethodType.genericMethodType(ptypeCount).form();
      assert (this != that);
      slotToArgTab = that.slotToArgTable;
      argToSlotTab = that.argToSlotTable;
    } else {
      int slot = ptypeCount; // first arg is deepest in stack
      slotToArgTab = new int[slot + 1];
      argToSlotTab = new int[1 + ptypeCount];
      argToSlotTab[0] = slot;  // argument "-1" is past end of slots
      for (int i = 0; i < ptypeCount; i++) {
        --slot;
        slotToArgTab[slot] = i + 1; // "+1" see argSlotToParameter note
        argToSlotTab[1 + i] = slot;
      }
    }
    this.primCounts = pack(lrc, prc, lac, pac);
    this.argCounts = pack(rslotCount, rtypeCount, pslotCount, ptypeCount);
    this.argToSlotTable = argToSlotTab;
    this.slotToArgTable = slotToArgTab;

    if (pslotCount >= 256) {
      throw newIllegalArgumentException("too many arguments");
    }

    // Initialize caches, but only for basic types
    assert (basicType == erasedType);
    this.lambdaForms = new SoftReference[LF_LIMIT];
    this.methodHandles = new SoftReference[MH_LIMIT];
  }

  private static long pack(int a, int b, int c, int d) {
    assert (((a | b | c | d) & ~0xFFFF) == 0);
    long hw = ((a << 16) | b), lw = ((c << 16) | d);
    return (hw << 32) | lw;
  }

  private static char unpack(long packed, int word) { // word==0 => return a, ==3 => return d
    assert (word <= 3);
    return (char) (packed >> ((3 - word) * 16));
  }

  public int parameterCount() {                      // # outgoing values
    return unpack(argCounts, 3);
  }

  public int parameterSlotCount() {                  // # outgoing interpreter slots
    return unpack(argCounts, 2);
  }

  public int returnCount() {                         // = 0 (V), or 1
    return unpack(argCounts, 1);
  }

  public int returnSlotCount() {                     // = 0 (V), 2 (J/D), or 1
    return unpack(argCounts, 0);
  }

  public int primitiveParameterCount() {
    return unpack(primCounts, 3);
  }

  public int longPrimitiveParameterCount() {
    return unpack(primCounts, 2);
  }

  public int primitiveReturnCount() {                // = 0 (obj), or 1
    return unpack(primCounts, 1);
  }

  public int longPrimitiveReturnCount() {            // = 1 (J/D), or 0
    return unpack(primCounts, 0);
  }

  public boolean hasPrimitives() {
    return primCounts != 0;
  }

  public boolean hasNonVoidPrimitives() {
    if (primCounts == 0) {
      return false;
    }
    if (primitiveParameterCount() != 0) {
      return true;
    }
    return (primitiveReturnCount() != 0 && returnCount() != 0);
  }

  public boolean hasLongPrimitives() {
    return (longPrimitiveParameterCount() | longPrimitiveReturnCount()) != 0;
  }

  public int parameterToArgSlot(int i) {
    return argToSlotTable[1 + i];
  }

  public int argSlotToParameter(int argSlot) {
    // Note:  Empty slots are represented by zero in this table.
    // Valid arguments slots contain incremented entries, so as to be non-zero.
    // We return -1 the caller to mean an empty slot.
    return slotToArgTable[argSlot] - 1;
  }

  static MethodTypeForm findForm(MethodType mt) {
    MethodType erased = canonicalize(mt, ERASE, ERASE);
    if (erased == null) {
      // It is already erased.  Make a new MethodTypeForm.
      return new MethodTypeForm(mt);
    } else {
      // Share the MethodTypeForm with the erased version.
      return erased.form();
    }
  }

  /**
   * Codes for {@link #canonicalize(java.lang.Class, int)}.
   * ERASE means change every reference to {@code Object}.
   * WRAP means convert primitives (including {@code void} to their
   * corresponding wrapper types.  UNWRAP means the reverse of WRAP.
   * INTS means convert all non-void primitive types to int or long,
   * according to size.  LONGS means convert all non-void primitives
   * to long, regardless of size.  RAW_RETURN means convert a type
   * (assumed to be a return type) to int if it is smaller than an int,
   * or if it is void.
   */
  public static final int NO_CHANGE = 0, ERASE = 1, WRAP = 2, UNWRAP = 3, INTS = 4, LONGS = 5, RAW_RETURN = 6;

  /**
   * Canonicalize the types in the given method type.
   * If any types change, intern the new type, and return it.
   * Otherwise return null.
   */
  public static MethodType canonicalize(MethodType mt, int howRet, int howArgs) {
    Class<?>[] ptypes = mt.ptypes();
    Class<?>[] ptc = MethodTypeForm.canonicalizeAll(ptypes, howArgs);
    Class<?> rtype = mt.returnType();
    Class<?> rtc = MethodTypeForm.canonicalize(rtype, howRet);
    if (ptc == null && rtc == null) {
      // It is already canonical.
      return null;
    }
    // Find the erased version of the method type:
    if (rtc == null) {
      rtc = rtype;
    }
    if (ptc == null) {
      ptc = ptypes;
    }
    return MethodType.makeImpl(rtc, ptc, true);
  }

  /**
   * Canonicalize the given return or param type.
   * Return null if the type is already canonicalized.
   */
  static Class<?> canonicalize(Class<?> t, int how) {
    Class<?> ct;
    if (t == Object.class) {
      // no change, ever
    } else if (!t.isPrimitive()) {
      switch (how) {
        case UNWRAP:
          ct = Wrapper.asPrimitiveType(t);
          if (ct != t) {
            return ct;
          }
          break;
        case RAW_RETURN:
        case ERASE:
          return Object.class;
      }
    } else if (t == void.class) {
      // no change, usually
      switch (how) {
        case RAW_RETURN:
          return int.class;
        case WRAP:
          return Void.class;
      }
    } else {
      // non-void primitive
      switch (how) {
        case WRAP:
          return Wrapper.asWrapperType(t);
        case INTS:
          if (t == int.class || t == long.class) {
            return null;  // no change
          }
          if (t == double.class) {
            return long.class;
          }
          return int.class;
        case LONGS:
          if (t == long.class) {
            return null;  // no change
          }
          return long.class;
        case RAW_RETURN:
          if (t == int.class || t == long.class ||
              t == float.class || t == double.class) {
            return null;  // no change
          }
          // everything else returns as an int
          return int.class;
      }
    }
    // no change; return null to signify
    return null;
  }

  /**
   * Canonicalize each param type in the given array.
   * Return null if all types are already canonicalized.
   */
  static Class<?>[] canonicalizeAll(Class<?>[] ts, int how) {
    Class<?>[] cs = null;
    for (int imax = ts.length, i = 0; i < imax; i++) {
      Class<?> c = canonicalize(ts[i], how);
      if (c == void.class) {
        c = null;  // a Void parameter was unwrapped to void; ignore
      }
      if (c != null) {
        if (cs == null) {
          cs = ts.clone();
        }
        cs[i] = c;
      }
    }
    return cs;
  }

  @Override
  public String toString() {
    return "Form" + erasedType;
  }
}
